450 Blade 450 3D Side-to-side slow tail wag

[helicc16]

Hi, RCH comrades. This heli was crashed once and has been repaired to like new conditions ( or so I thought ). It flies fairly well except for the slow side-to-side tail wag ( about 2 inches at the tip of the boom ).

The tail holds well during climb-out and pirouette stops are nice and crisp. The stock gyro is set to factory specs, and I did increase gyro travel setting a tad bit. tail servo is in good order. Belt tension is good. In general, no observable mechanical problems. Can't figure out what causes such tail wag. It makes the heli feel unstable. Please advise.

 

[Westy]

hmmmmmm interesting ...... have you tried to reset your mechanical servo 90 and o blade pitch and then set up the gain? Just a thought..... Tail Blades balanced and Cg'd?

what is the gain set to ? how far is the tail servo ball from the servo pivot point? ....


Oh oh oh .... is it getting full travel from side to side on the tail slider? .... you have not got a DR setting stopping the gyro grabbing all the servo stroke it needs?

 

[RCD]

There is the possibility it got internally damaged when it crashed. Is the servo working fine?

 

[helicc16]

Yes. It got full travel on the tail shaft. I've replaced the tail servo and the gyro with Align GP790 and DS420. The said wag is largely gone but still slightly visible. As I said before, it is a very slow lateral drift. That bothers me less than before but it still does to a small degree. It may be that I am not content with anything less than a solid tail hold. LOL

I haven't never bothered to balance the tail rotor, thinking the its tiny weight won't make much of a difference for a 450 size heli. I might be wrong.

Anyway. Thanks your suggestions, gentlemen

 

[Tony]

There will always be a drift in the tail, no matter what you use. If you think about it, if your sitting in a chair blindfolded, and someone very slowly starts to turn the chair, you will never know it. Same goes with teh gyro. It doesn't have any eyes, or better yet, gps to help hold it in it's current position. So even though ti's doing its best job to hold the tail, it can only do so much.

In all reality, the heli is meant to fly forward. With that flight pattern, it will always know where the tail is supposed to be. Sitting in a hover, it's not quite sure what to do with the very small movement that it can't detect.

 

[RMB677]

Check the tail belt drive gear. When my gear went I started to get some strange behavior on the tail till I lost all rudder completely.

 

[Lee]

Check for mechanical binding. Your tail assembly from the servo link, all the way to the blade grips should be smooth. A good way to check this, is to hold the heli on its end (nose pointing to the sky) with the link to tail servo disconnected. If you lift the control rod up by hand to the full extent of the tail slider, and release it, it should drop freely, so the pitch sldier hits the opposite end of the tail shaft.
If this doesn't make sense, i can add video tomorrow.
Also make sure your gyro frequency is matched to the tail servo ie 1520-1520 or 760-760

 

[helicc16]

Lee,
I've just tried what you suggested. The linkage is butter smooth.

Roger,

All belt gears are fine.

Tony,

I like your analogy. I forgot that all gyro have a inherent drift, even the solid-state ones.

I guess I need to stop being perfectionist on this one.

 

[Tony]

I was the same way man. No matter what, when I was hovering, the tail was always moving. Even if a little, it was moving and I tried everything to get it out. But, then I got into FF and it all went away and the tail held the pitch pumps, flips and so on perfectly every time as long as you have a good gyro and servo back there.